After I visited Saudi Arabia, I stayed in Qatar for 2 days (flying Djeddah - Doha).
Here's what I did:
D1: rent a car, drive to Barzan Towers (worth a look but nothing special), Al Zubarah WHS (see my review, took 2 tries), Al Ruwaida archaeological site (saw the sign but no way to enter from the main road, lots of construction going on), Al Jassasiya East Rock Art Site (worth a short stop but petroglyphs hard to see). Back in Doha, see the spiral mosque (modelled after the one in Samarrah) at night and visit the Souq Waqif.
D2: lazy morning because everything is closed on a Friday til 2pm (even the metro), stroll along the Corniche to see the Pearl monument and the wooden boats, then have lunch at the Souq (most restaurants are open on a Friday), and finish at the excellent National Museum.

I'm done with all the small Gulf states now. Historically, Bahrain probably is the most interesting. Qatar doesn't add much if you already have been to the UAE, but it is newer, has fewer highrise buildings and the center of Doha even has a somewhat European feel (it must be the combination of stone-paved streets and pedestrian traffic lights!).

Renting a car is easy (cheap daily rates, cheap gas) and the main highways are good, but traffic in Doha itself is very busy and it can be hard to find a parking spot (so I used the metro to get around there and to the airport).

I think I will do all the remaining Gulf States (after my UAE trip recently) around 2030. I want to wait until the Qatar–Bahrain Causeway (30 minutes between countries) and perhaps the Gulf Railway mega project are completed. Also by that time hopefully Kuwait has its first WHS. To include more iconic WHS, I would likely include (time permitting) a longer sojourn in Türkiye at the start or extend the end of the trip to include Mumbai.

About a 2-week trip:
- Oman (7 days)
- Qatar (2 days)
- Bahrain (3 days)
- Kuwait (2 days)

I would add a few more days for Oman though!

I think that is perfect advice if you wished to see the wider country of Oman. If I go to Oman, I am likely only visiting Muscat, Rustaq, and Nizwa. I am not really a completist! I don't think I would bother with the Archaeological Sites of Bat, Al-Khutm and Al-Ayn let alone further Southwest to The Land of Frankincense WHS. I think 7 days would do for these areas, based on the reviews I read here.

2 WHS:
- Aflaj irrigation system
- Bahla Fort

2 TWHS:
- Al Dimaniyyat Islands Nature Reserve
- The Forts of Rostaq and al-Hazm

Without risking getting further off-topic regarding Qatar. For me its quality over quantity and that also means comprehensive (quality) visits rather than quick ticks. My spouse has certainly influenced my thinking on this. This is why the Qatar–Bahrain Causeway is so appealing to me as a traveller. It's hard for me to justify a trip to Qatar and Bahrain separately or together right now when the travel distance currently remains counterintuitive. Bahrain is widely considered more interesting within this community than Qatar, at least in regards to World Heritage. So how much am I willing to pay (time/money) to visit the Al Zubarah Archaeological Site? Not much. However, when the causeway is complete Qatar and Bahrain are 30 minutes from each other, the effort needed for a modest WHS such as Al Zubarah Archaeological Site is now substantially more worthwhile. The same goes for the other WHS in Oman, I am NOT making the effort to visit Qalhat! I enjoy the chase of the proper obscure WHS, but my spouse is going to want out of that rent-a-car if I am trying to drive to a relatively modest CLOSED archaeological site on bumpy dirt roads.

The WHS worth depends on its accessibility?
Concerning Oman, Qalhat is not the only intersting place in Oman, it's closed to Sour port for example and on the road of the Wahiba sands desert, even if theses places are not inscribed on the WHS list. You also have several "wadis" like Wadi Shab, a very nice place.

I think the experience of visiting 2 countries (Qatar and Bahrain) and their capitals (Doha and Manama) and not working too hard for a mildly interesting WHS pays off for the time and money saved. That "time" saved also often leads to less-rushed, more comprehensive world heritage experiences. I certainly find value in every visit to a WHS. Visiting Bahrain and Qatar's world heritage sites and getting an understanding of the country at large, I think is a valuable experience. I cannot help but appreciate the coming reality of cutting travel time from around 5 hours to 30 minutes between the two nations.

I certainly value accessibility, but I would not say that affects the rating I place on a WHS. There are also so many incredible remote WHS, in which the journey is part of the reward (that is not the case in Bahrain/Qatar). I will certainly research more about Oman before I travel there, my knowledge of the country is limited. Wadi Ash Shab looks wonderful.